The objectives of this research proposal are to determine the sequence of events involved in the development and functioning of a chemotactic signalling system in the slime mold amoebae, Dictyostelium discoideum. This problem will be approached by a combined genetic and biochemical study of the major membrane-mediated events involved in cell differentiation and aggregation. Emphasis will be placed on understanding (1) the factors which regulate adenylate cyclase such that cAMP (the chemoattractant for slime mold amoebae) synthesis occurs in the form of pulses; (2) the molecular events which lead to the developmental increase in the enzyme; (3) the mechanism by which imposed pulses of cAMP affect both of these phenomena. Many of our studies will be aided by the various mutants which we have isolated and partially characterized, and we will continue to search for other mutants defective in the chemotactic signalling system.